[PATCH] D56466: [CodeGen] Clarify comment about COFF common symbol alignment

[Shoaib Meenai via Phabricator via cfe-commits]

smeenai updated this revision to Diff 180771.
smeenai added a comment.

Refer to link.exe, and then also refer to other linkers in the second half of the comment to match


Repository:
  rC Clang

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56466/new/

https://reviews.llvm.org/D56466

Files:
  lib/CodeGen/CodeGenModule.cpp


Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -3761,8 +3761,12 @@
       }
     }
   }
-  // COFF doesn't support alignments greater than 32, so these cannot be
-  // in common.
+
+  // Microsoft's link.exe doesn't support alignments greater than 32 for common
+  // symbols, so symbols with greater alignment requirements cannot be common.
+  // Other COFF linkers (ld.bfd and LLD) support arbitrary power-of-two
+  // alignments for common symbols via the aligncomm directive, so this
+  // restriction only applies to MSVC environments.
   if (Context.getTargetInfo().getTriple().isKnownWindowsMSVCEnvironment() &&
       Context.getTypeAlignIfKnown(D->getType()) > 32)
     return true;


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